Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.
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Thanks for the tip! I’ll have my team look into it.
Hi, I thought I would suggest that you put question 6 before questions 4 and 5, rather than after. For both 4 and 5 my son, but in both cases explained, not unreasonably, that he was considering air resistance. Obviously air resistance wouldn’t make much of a difference in each case, but it’s not a bad thing if kids pay attention to details at that level.
Hmmm… you’re right. That is really one short tree! 🙂
Hi Aurora,
We just read the conversation about how the biologist is “aiming” hs gun and whether he knows enough to aim higher than his target or not. That was good. But, since the monkey is hanging from a branch on a tree, we were assuming that the monkey was higher than the biologist. Therefore, the tranquilizer would miss (even if he aims straight at, and not adjusting for “aim”) because the monkey is falling, but the bullet would have inital upward momentum. Or this is one short tree.
Nathan & Rosie
Here’s a bit more information about bending light you might find useful:
Prior to the solar eclipse experiment, Einstein’s theory of General Relativity had been untested and more of an interesting idea. If you really think about it, if light did not have mass, then how could it be affected by a force, such as gravity? Isaac Newton stated that gravity is depends on the mass of two objects, so light could not be bent by gravity.
Einstein’s General Theory of Relativity approaches the problem differently. Einstein used the analogy of an elevator to explain his thoughts on the equivalence of inertial mass and gravitational mass, saying that the sensation of being held to the Earth by gravity would be the same as being pulled through space while in an elevator with a constant acceleration of 9.8 m/s². In either case one would be held to the floor of the elevator with a seemingly identical force, and would not be able to tell the difference (thus, the two situations would be considered relative).
Providing that Einstein’s equivalence principle (the assertion that inertial mass and gravitational mass are equal and interchangeable) is correct, the elevator analogy can also be used to explain why gravity bends light.
How Einstein’s Principle Works
Consider an elevator motionless in space (so that there is no gravity inside and any occupants are in “freefall”). This elevator has a pin-sized hole in the wall, through which a tiny beam of light enters, creating a speck of light on the opposite wall, directly across from the hole (if one measured the distance from the floor of the elevator to the hole and to the speck of light, it would be equal).
Now, if this elevator began to be pulled forward through space, the inertial mass would pull the occupants to the floor of the elevator (mimicking the pull of gravity), and something peculiar would happen to the beam of light:
As the elevator’s acceleration increases, the prick of light will appear to move downward, for in the time it takes for the light to travel from the hole to the opposite wall, the elevator would already have moved forward slightly (though it would have to be moving rather quickly for this effect to be at all noticeable).
In other words, because of the motion of the elevator, the beam of light would “bend” as it enters the elevator. Now, carrying this thought through to its conclusion – remember that the occupants of this elevator would have no way of knowing if the sensation they are feeling is caused by the elevator’s inertia or by some gravitational force (it could feel to them that they are on the surface of the Earth), so to these people, the bending of the beam of light appears to be caused by gravity.
According to Einstein and his General Theory of Relativity, these two situations are identical, and thus, gravity can indeed bend light.
By Isaac McPhee
That’s a really great question. Einstein predicted that light could be bent by gravity. If Einstein was right, then the sun not only bends light but also space and we could observe this by looking at the stars behind the sun (the most massive object we had close by).
So if the sun were between us and certain stars that we know the exact positions of, then we can expect to see the light from those stars being bent as it passes the sun on its way to us here on earth. When this happens, the stars should appear shifted by a certain (tiny) amount that was measurable.
The trouble is, the sun is sooo bright that we can’t see stars during the daytime! They solved this problem when Sir Arthur Eddington photographed a solar eclipse in 1919 and another in 1922 and found that the stars were exactly where Einstein said they should be and not where Newtonian physics predicted. Which changed the way scientists were thinking about not only gravity but light as well.
What experiment proved that light was bent by gravity?
Yes, light does bend because of gravity – that’s how we detect black holes (it’s called gravitational lensing) and large objects (ones that are WAY bigger than the Earth). Black holes can cause streaks of light on your film where a point of light should be, and even double images of the same galaxy. A photon does have mass, albeit a very very small amount of mass. Think of a photon as something that can travel like a wave but interact with things (gravity, for instance) like a particle. The problem people have with the photon (packet of light) is that they try to cram it into a model of something that acts like either a wave or a particle, when really it acts like a photon, which is both and then some. You can learn more about it in Unit 7: Astrophysics. Does that help turn your brain into a pretzel?
Your comment really made me chuckle because we actually had a very similar conversation when we were first discussing the question. First the kids wanted to know why a a biologist would want to study a monkey. Then when someone mentioned a laser site, Ben suggested that you would still need to fire higher than the intended entry point “because the bullets path curves but the laser light doesn’t. Wait, Mom, DOES the laser light bend? ”
So, if I thinking this through correctly, Newton would say no it doesn’t, because light doesn’t have mass, but Einstein would say yes it does bend. ????? So, we’re wondering, how does light behave on Earth. If you were using a super intense laser pointer, how long would the beam need be (how far would it need to shine) before you noticed a bend in the light? Is it even possible to create a beam that intense?
I’m still trying to wrap my mind around the questions he asks and have no idea how to try to explain the answer to a 9 year old.
Want to field this one? 🙂
Cheers,
Tammi K
You’re absolutely right – thanks for the clarification. I am guessing our biologist was too busy learning about plants than guns, so you’re right – he probably has no clue how to use one! (And why a biologist would hunt a monkey is really a brain twister in itself…) Maybe I should modify that to say ‘laser sight on the monkey’s shoulder’. Would that be better? 🙂 Sounds like you already have a good grip on gravity!
I think he focused on the word ‘aimed’ which he took to mean ‘pointing the gun so the bullet will HIT the target.’ NOT ‘point the gun directly AT the target.” (Pointing AT the target will cause the scenario you describe. Whereas, I believe he was thinking ‘aiming for the target.)
After hearing your reply he explains: “What I meant was, if the biologist wanted to hit the monkey on the shoulder, he would have to point the gun a little bit higher than the monkey. The further away the monkey is, the higher he would have to point his gun. If he points right, straight at the monkey, he doesn’t know anything about guns!”
The monkey and the dart fall downward at the same rate of speed. So the dart would hit exactly where the biologist aimed! In fact, if the monkey didn’t let go, the dart would have hit lower then the biologist aimed. It doesn’t have anything to do with being a ‘bad shot’ but rather how gravity affects the bullet.
Regarding the biologist and the monkey, Ben (age 9) asks: Does this mean the biologist was a bad shot? If he was firing the same gun from the same distance at a solid target that couldn’t fall instead of a monkey that could, he would have missed the bull’s eye on the target.