"In science, "fact" can only mean "confirmed to such a degree that it would be perverse to withhold provisional assent." I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms." -Stephen Jay Gould
Those of you who follow me on either google+, facebook or twitter know that I sometimes post interesting articles about science from around the world, including this very good article about myths about outer space, from the often-entertaining cracked.com. So, as you can imagine, I was (at first) very excited when I saw this article last week over there.
(Image credit: cracked.com.)
Imagine my disappointment when I read this, and realized that the “6 Scientific Discoveries that Laugh in the Face of Physics” turn out to all be things that physics understands and can explain! Looking at it today, you can see that well over 1,000,000 people have read this, so let’s see if we can’t get the correct information back out there to as many of them as possible. Without further ado, let’s take a look at these six scientific discoveries, and do our best to get it right!
(Image credit: Miloslav Druckmuller / SWNS.)
6.) The Sun Can Make Stuff Hotter Than Itself.
Above is the Sun’s Corona, visible only during a total solar eclipse, as shown above. And while the surface of the Sun is very hot, at something around 5800 K, the Corona comes in at temperatures over one million Kelvin. Mysterious, mind-boggling and inexplicable by the laws of physics, right?
Except that temperature is not the same thing as heat! The Sun’s surface is much, much denser than the incredibly rarified corona, so that even though the Sun’s photosphere is less than 1% of the corona’s temperature, it emits energy at a rate that’s over 40,000 timesthe amount required to heat the corona up to it’s high temperature. We even think we know why: the wave heating theory, where energy can be transferred over long distances from the solar interior to the corona.
(Image credits: Robert Krampf; stills taken from MetaCafe.)
Remember what temperature is: a measure of the mean speed of the particles. Similar to how two balls — a tiny one and a very massive one — dropped one-atop-the-other will lead the tiny ball to rocket upwards at an incredible speed, the problem isn’t getting a few particles to have a very large speed. The problem also isn’t unique to the Sun; if we take a look at Earth’s upper atmosphere, where it gets really rarified (above 80 km), we find that it does the same thing in terms of temperature!
(Image credit: Earth’s Atmosphere, from kowoma.de.)
The problem is that we associate temperature with heat in our minds, but the “very high temperature” corona contains almost no heat! But if we look in terms of heat, the Sun’s photosphere contains much more than the corona; the corona merely reaches higher temperatures.
(Image credit: © 1968 George Resch - Fundamental Photographs.)
5.) When You Look Closely, Gravity Stops Making Sense.
The article laments that gravity is so mind-numbingly weak. How dare you, gravity! And it’s true; weaker by something like 38 orders of magnitude than the electromagnetic force, even your puny comb can outdo the gravitational pull of the entire Earth when it comes to lifting certain objects. But this isn’t a mystery, it’s an empirical fact of nature!
(Image credit: Joan Adler, Technion, Israel.)
The standard model of particles and interactions can do a whole lot, but one of the things it can’t do is explain why the fundamental forces are the strength that they are. Neither can general relativity, our theory of gravity. As you can see, gravity is very, mind-numbingly weak, even compared to the weakest other force.
But whether you look close or far, at something as massive as a supermassive black hole or as tiny as a laboratory mass, general relativity still gives the correct answer to everything. The only argument that one could even make that “when you look very close, it stops making sense” would be to go down to the smallest scales we know of.
(Image credits: Ultra-Cold Matter Research at William & Mary.)
Only, with gravity, we can barely make it below the millimeter-scale before it becomes too difficult to measure. And we can measure the effects of gravitation down to these sub-millimeter scales: it obeys general relativity just fine, thank you. Perhaps someday, we’ll reach down to quantum mechanical scales and find that our classical theory of gravity, general relativity, is insufficient. But in theory, general relativity is good all the way down tothe quantum limit of the Universe, and we have yet to find an experiment or observation that contradicts it.
(Image credit: Pioneer 10 by Don Davis, for NASA.)
4.) Satellites Speed Up for No Reason.
So, get this. In the 1970s, we launched two probes — Pioneer 10 and 11 — into the outer Solar System. As we tracked their positions over many decades, we knew exactly what to expect. After all, we know the laws of gravity, we know the masses and positions of the Sun and all the planets, and we should be able to predict the spacecrafts’ motions flawlessly. Except we saw a small — but definitely non-negligible — acceleration back towards the Sun!
Immediately, a number of spectacular explanations arose. Gravity is wrong! The solar system is full of dark matter! Spaghetti! Except among most astrophysicists (like me), anotherexplanation arose: maybe the asymmetric spacecraft is being heated (and is radiating) asymmetrically.
(Image credit: NASA / Francisco et al., retrieved from Jennifer Ouellette.)
For decades, the debate raged, as much as anything where one side doesn’t really give the other side much credibility can rage. And then last year, it was definitively measured that the “anomalous acceleration” is not constant, but decreasing, and hence in total agreement with the theory that it’s due to the thermal effects that the astrophysicists pointed out. So yes, cracked, satellites speed up for no reason, but only if you ignore the actual reason.
(via Defending Physics Against Cracked.com : Starts With A Bang)