Blinded by Science blog #5: Should I turn the AC or heat off in my home when I'm away at work during the day? Do I save any energy and $ on cold and hot days by doing this?

Well everyone, it’s that time of the year again.  The birds are singing, the sun is shining, and copious amounts of fluid are leaking from my nose and eyes (allergies suck!).  That’s right; spring has arrived (and hopefully gets to stay for awhile, allergies and all).  In honor of the changing of the seasons, I’m going to answer a question from a friend of mine that is pretty topical (plus it could save you money and everyone likes that).  Chris H. asks, “Should I turn the AC or heat off in my home when I’m away at work during the day?  Do I save any energy and $ on cold and hot days by doing this?”

Well Chris, to answer your question, we’re going to have to look to the physics of heat/energy transfer which is a topic I haven’t thought about since I took AP Physics in high school (Sorry Mr. Thompson!)*.

Let’s imagine a simple scenario.  You have a house you wish to be heated to 75°F from a starting temperature of 35°F and the outside temperature is 35°F.  Your heater turns on and begins to heat the house (depending on the heater, it will probably use natural gas or electricity).  The temperature in the house eventually reaches 75°F and the thermostat sends a signal for the heater to shut off.  And now, because no place has perfect insulation, heat begins to be lost to the outside (heat is transferred from high temperature to low temperature).  This causes the temperature in the house to begin to drop.  When it does, the thermostat sends a signal for the heater to turn back on and bring the temperature back up to the set point.  When the temperature again reaches 75°F, the heater is shut off and heat again begins to be lost to the outside**.  This series of events will continue as long as nothing changes (like the outside temperature reaching 75°F or you turning off the heater or you changing the set point).

This pattern uses up a lot of energy (and when you are paying the heating bills, a lot of money) and it makes sense when you are actually in the house (let’s assume the temperature you set the thermostat at is the lowest temperature you feel comfortable at since you could otherwise save some money by just lowering the set point).  But the question asks about when you are not in the house and here is where physics comes in.  Because the amount of heat lost to the outside is a function of the difference in temperature between the inside and outside, it actually requires more energy to keep the temperature at 75°F than it would at, say, 65°F and you would actually have a slower heat loss at the lower temperature (so says the Department of Energy).  I realize this is counter-intuitive, but it is true.  In fact, according to that link, setting the thermostat 10-15° back for 8 hours a day (like when you are at work or even sleeping) can translate to a 5-15% savings on your heating bill.  This is why using a programmable thermostat is such a good idea.  You can set it to automatically lower the temperature during the times you are away and don’t need the inside to be so warm and to raise the temperature again when you get back (Pro-tip: have the thermostat start raising the temperature 30 minutes or so before you get back from work or wake up in the morning.  That way the house won’t be as cold when you get home/wake up).

And this takes us back to the specifics of the original question.  If lowering the temperature set point by 10-15° can save a good amount of money, what about just turning off the heater when you are at work?  Yep, just completely turning it off would save you more money . . . with an important caveat.  In the winter, if you let the house get too cold, your water pipes could freeze.  Believe me; you don’t want that to happen.

So it would make the most sense to just set the temperature lower than normal instead of turning off the heater altogether.

“But wait!” you say, “Doesn’t setting the thermostat lower just mean the heater has to work harder to get back up to the temperature I want when I get home?”

“Oh you,” I say as I chuckle a little and pat you on the head, “A heater doesn’t work ‘harder’ if there is a greater difference in starting temperature and set temperature.  It just works longer.”  This is the same reason why jacking up the thermostat doesn’t actually make the room heat up any faster (a fact, I must admit, I was unaware of before researching for this blog post).

In fact, today’s heaters are more energy efficient if they work for longer periods of time at once.  This means it will actually take less energy to raise the temperature a large amount all at once as opposed to keeping the temperature at the set point all day.  And since energy in this case translates to money you spend, it also means you spend less money.

And just so we’re all on the same page, everything I said also holds true for lowering the temperature in the summer with the A/C.

So yes, you can definitely save money by turning off the A/C or heater (Well, as I said, just turn down the heater in the winter.  Don’t turn it all the way off) when you are not at home.

*I asked my friend Jeff M. to look over my answer since it has been awhile and he studies physics.  He said it “looks fine” which makes me feel better since that means I didn’t just make it all up.

**Just to be clear, in real life heat would be lost the entire time, not just when the heater is off.  But the amount of heat the heater is generating is greater than the amount of heat lost to the outside which is why the temperature in the room increases.

Blinded by Science blog #4: How much of the human genome is the same from person to person and how much makes up what is unique in us?

Hello and welcome to another wonderful addition of Blinded by Science™.  Hmmm.  I wonder.  Does just adding the “™” symbol actually DO anything?  Probably not.  I feel like there should be paperwork involved.  I mean, there’s always paperwork involved.  Ah well, I could look into it, but it’s probably nothing I have to worry about right now.  Anyway, where was I?  Oh yes . . . welcome to another wonderful addition of Blinded by Science.  Today’s contestant comes to us all the way from sunny and warm . . . no cloudy . . . no snowy . . . no sunny again but colder this time . . . no rainy . . . ARGH never mind!  Today’s contestant comes from Ohio, a place where all four seasons can occur in a single day, unless you are talking about roadwork season, because that lasts forever (and you’ll still get a flat tire from the potholes).  Chris G asks, “How much of the human genome is the same from person to person and how much makes up what is unique in us?”

Well, since this is the first real biology-related question that I will try and answer, I am going to go all out with the answer.

As I hope you are already aware, DNA is made up of four different base pairs: adenine, guanine, cytosine, and thymine (commonly referred to as A, G, C and T).  The order of these bases makes up the genetic code.  It doesn’t seem like there would be enough information held in only those four “letters” to code for any sort of life, let alone life that is as varied as exists on Earth, but there is because of two important facts.  One is that the sizes of genomes are big.  In the case of humans, our genome contains approximately 3 billion base pairs, so the amount of different combinations is 4^3000000000 (a REALLY BIG number), though the amount of biologically feasible combinations is less.  What I mean by this has to do with the second important fact, the way in which DNA codes for proteins.

For life to exist, the information stored in DNA must be expressed in a form that does work (the pattern on a key doesn’t do anything by itself, but put it into its corresponding lock and now you can open a door).  In this case, genes are converted into proteins (via an RNA middleman since DNA does not leave the nucleus)* which then do basically everything necessary for life (need a specific molecule broken down, there’s a protein for that; need some ions transported across a membrane, there’s a protein for that; need to rebuild your muscle fibers after that really intense workout, proteins do that too).  This translation from RNA to protein occurs at a site called the ribosome.  The ribosome “reads” the RNA strand (which does not contain the thymine base but instead has uracil) until it comes to a specific sequence of three RNA bases (AUG) that it recognizes as the place to start synthesizing the protein.  Called the “start codon”, AUG also codes for the amino acid methionine which means all proteins start with methionine.  The ribosome then moves onto the next three bases (next codon) and depending on the arrangement adds the corresponding amino acid (AUGCCCCAC becomes methionine-proline-histidine).  Each amino acid has its own specific physical properties which affect the overall activity and function of the protein.  This is how proteins are made and why I said there are fewer biologically feasible combinations of bases (having a genome that only consists of adenine means you would never have ANY start codon, and even if you did, all the proteins would have be made up of the same amino acid).  When the ribosome reaches one of three specific codons known as the “stop codons” (UAA, UAG, or UGA), it terminates the synthesis and the newly formed protein is released to go do its job.

There are 64 different codons which correspond to 20 different amino acids (well 61 since the stop codons don’t code for amino acids) and depending on where the stop codon occurs a protein could be only a few amino acids in length or hundreds of amino acids long.  This is how only 4 bases are able to code for such an enormous variety of proteins.

Now what was the point of all that?  Honestly, I don’t remember.  Whoops.

In all seriousness, there was a point to that little biology lesson.  We’ve all heard of mutations, where something causes a change in the genetic code.  Sometimes those changes are just a switch of base pairs (AGA becomes ACA).  This can cause problems when the change causes a different amino acid to be inserted (AGA codes for arginine while ACA codes for threonine) which might end up changing the properties of the protein.  Other times, the change could be “silent” (both AGA and AGG code for arginine).  Basically, as long as mutations are not selected against, they can be present in the genetic code of some members of a species.

Mutations can also occur in regions of the genome that do not code for genes (there are many other parts to the genome than just the protein coding genes, but that would likely be better served as a topic on another day).  Again, as long as these mutations are not selected against, they can persist in some members of a species.

And this brings me back to the question of today’s blog (finally).  Mutations are just one way that members of species can differ genetically (other ways such as epigenetic changes or copy number variations also exist).  So taking this all into account (well as much as we can with our current technology as certain parts of the genome are still hard to read), it is estimated that humans are 99.5% similar to other humans (as a point of comparison, humans are estimated to be between 96% to 94% similar to chimpanzees based on genetic analysis)**.  So we are really similar to one another, but not identical (not even identical twins are 100% similar genetically), which I think is a good thing.  Wouldn’t life be so much more boring if we were all the same?

*This is an extremely simplified version of events.  I mean, what would life be like if there weren’t lots of exceptions to the rule?  There are some cases of some RNAs having biological activity on their own without being translated into protein first.  We don’t need to get into that today though.

**I really wanted to add a mention of the genetic similarity of viruses within the same species because it is so much less than human similarity.  I think I recall having been taught either 60% or 70% similar (though it could still be much lower), but I could not find a citation that mentioned it.  Suffice it to say; based on the amount of genetic similarity between some viruses of the same species, humans and chimpanzees (as well as other types of apes) would be members of the same species.  Think about that.

Blinded by Science blog #3: How serious of a problem is our supply (or lack thereof) of clean water? I have been hearing about the severe droughts in CA and around the globe. I thought water was a renewable resource so I am confused as to what the real issue is.

Today’s question comes from a reader that has been around since the very beginning (I know this because he liked the Facebook post about my first blog entry, and as we all know, that means he read it).  Ben S. asks, “How serious of a problem is our supply (or lack thereof) of clean water? I have been hearing about the severe droughts in CA and around the globe.  I thought water was a renewable resource so I am confused as to what the real issue is.”

What a topical question.  Hence the quick turnaround from when I received this question to my posting this entry.

First off, let’s begin by highlighting the importance of water.  It’s VERY IMPORTANT!

Now that I’ve gotten that out of the way, we can move on to . . . what?  You would like a little more?  Well okay, but just a little.

Water is absolutely essential to life as we know it.  Not to get into deep and complex examples, but the chemistry that allows life to exist absolutely requires water and its very specific set of physical properties.  In fact, the presence of water on any planet (or moon if it is big enough) is one of the most important factors astronomers look for when searching for extraterrestrial life (which could end up being anything from microscopic bacteria to Wookies . . . or Klingons . . . or Daleks . . . or Xenomorphs . . . or even Sandworms).

Anyway, the human body requires water intake every day and this water has to be safe to drink (lacking disease causing microorganisms and toxic elements).  Water that fulfills this requirement and is therefore safe to drink is called potable water.

Water, water, everywhere,

And all the boards did shrink;

Water, water, everywhere,

Nor any drop to drink.

- Samuel Taylor Coleridge, The Rime of the Ancient Mariner, 1798

As I’m sure you remember from elementary/middle school, water covers around 70% of the Earth’s surface.  That’s an enormous amount of water.  Plus as the question mentions, water in general is a renewable resource (the water cycle).  Unfortunately, the vast majority of the Earth’s water is in the oceans and seas, and as anyone who has been swimming in the ocean knows, the water is very salty.  So salty, in fact, that drinking it actually dehydrates you.  So of all the water present on Earth, the vast majority (close to 98%) is unfit for human consumption or agricultural use based on salt content alone.  That leaves a small supply of water available for human use (be it drinking, irrigation/farming, or industrial use).  This water is accessible via streams, rivers, lakes, or aquifers.  Aquifers are basically layers of rock in which water is found.  Depending on many factors (such as depth, mineral content, salt content, etc.), this water can be used to supply human needs* (plus you do not get the evaporative loss like you do from surface supplies nor are you as likely to have as large an environmental impact from accessing aquifers as you do from building a dam).  In fact, water from aquifers supplies much of the freshwater humans use, including the water used in California.

California is one of the biggest agricultural producers in the world (I’ve seen 5^th largest, but I haven’t been able to verify it) and it produces “nearly half of US-grown fruits, nuts and vegetables.”  All of that farming requires a substantial amount of water, much of which is supplied by aquifers.

Map of aquifers from the US Geological Survey website.

This brings us back to the water cycle.  Aquifers are naturally replenished from precipitation over time, but depending on the depth of the aquifer, this process can take years, or centuries, or even millennia.  So if humans end up using water faster than it can be replenished (especially during drought conditions in which precipitation rates are decreased), you can imagine that we will eventually have a problem.

And that is exactly what is happening in California and other places as well.

Remember how I said that the Earth has an enormous amount of water, but that it is too salty for human use.  Well, we do have the technology to remove the salt and therefore create freshwater for use.  Unfortunately this technology, desalination, is much more expensive than just pumping water from aquifers (it costs around $800 to $1400 per acre-foot of desalinated water produced) and it isn’t able to come close to meeting necessary demand for freshwater.  At least not until the technology improves.

So to summarize the answer to your question Ben:

1)  Water, itself, is a renewable resource of which there is an extremely large supply.

2)  Unfortunately, human uses (including consumption) require freshwater, of which there is a much smaller supply.

3)  Aquifers are a major source of freshwater but if our use exceeds their renewal, they will eventually run dry.  Droughts will exacerbate this problem.

4)  Eventually desalination could alleviate this problem, but until then, we are pretty much at the mercy of Mother Nature.

I hope this answers your question.  If you have need of any clarification or follow-up, leave a message in the comments below.

*Though I didn’t mention it, this water still needs to be purified so that pathogens are removed and it is safe for human consumption.  For a lot of places, access to clean water is a major problem, which is why droughts in those areas can be so devastating.

Blinded by Science blog #2: Why doesn’t the sun always shine and where does it go?

Hello and welcome to the second entry of my science blog, “Blinded by Science.”  In today’s installment, I will again answer a question posed by my cute, three-year-old godson, G.

G asks, “Why doesn’t the sun always shine and where does it go?”

Another astronomy question means I will have my work cut out for me convincing him to go into biology.  Though he has said he wants to “be a doctor like T” (photographic proof below), so it is a challenge I am willing to accept.  I’m thinking copious amounts of bribery while he grows up and possibly some Diet Coke and Mentos (which doesn’t really have anything to do with biology but would still be cool to do).

See.  He looks pretty good in a lab coat.

When asked why he thought the sun doesn’t always shine, he answered that it goes to sleep at night, like him.  Compared to his thoughts on the moon question he asked last time, this answer is less plausible but so much cuter!

Well G, the sun doesn’t really go anywhere.  The Earth is really big and constantly spinning in space.  So sometimes the part of the Earth that you live on is facing the sun (daytime) and sometimes it is facing away from the sun (nighttime).  The cool thing is even if you can’t see the sun shining, someone else in another part of the world can.

Let’s ask your mom to help with another demonstration.  This time all that’s needed is a flashlight to be the sun.  Go stand in the middle of a dark room and have your mom stand a little behind you with the flashlight pointed at you.  Ask her to turn it on.  You can’t see the flashlight because the back of your head is blocking the light and you don’t have eyes in the back of your head (only mothers have eyes in the back of their head, which is why they always know what you have done . . . always).  While standing in the same spot, slowly turn to your left.*  Soon you will begin to see the flashlight (1).  This is what happens when the sun rises in the morning.

As you continue to turn, you will soon be able to see the whole flashlight as you look right at it (2).  This is what happens around noon when the sun is high in the sky.  Eventually you will start to see less of the flashlight (3).  This is what happens when the sun sets and it is getting close to your bed time.  Finally you get back to where you started and the flashlight is behind you.  This is why it becomes dark during nighttime.  But the flashlight is still shining on the back of your head, just like the sun still shines on the other side of the Earth.

*This is actually the direction the Earth spins.  In other words, if you were an observer in space looking straight down over the North Pole, you would see the Earth spin counter-clockwise.