Is Neil DeGrasse Tyson credible?

[BadgerBadger92]

I just learned recently that Michio Kaku is a bad source to learn physics. I was wondering if the same applies to Tyson. I love the series Cosmos, and was wondering if this series is credible.

 

[Ibix]

Generally the problem with all popsci is that you can learn someone's presentation of facts about physics, but that is not the same as learning physics. It is very difficult to teach any advanced physics coherently without the underlying maths, precisely because it's talking about circumstances where we have no "common sense" understanding and the maths is the formal replacement for it. It's what ties all the words together and gives them clear definition.

Popsci also has a marked tendency to present the latest harebrained idea someone's come up with as "scientists now think that..." as if there were consensus even when there is none. Most ideas in science are wrong. Only a very few survive rigorous testing to become accepted science.

If you don't want to learn enough maths, what I'd look for in a populariser is a clear idea of just how speculative what they're talking about is. And a willingness to say "I don't know".

 

[DaveE]

I can't imagine how one would learn physics from his appearances. It's not bad, it's sort of non-existent, IMO. He's very entertaining, I guess, but he never actually says much of substance. I don't think he's wrong too often, but I haven't heard him a lot. I find him a bit annoying, personally, along with most all of the "TV physicists". They all cater to an audience that doesn't actually want to study physics, which is OK, I guess. After all, I like to read about black holes even though I know nothing much about GR and don't want to if it means real work. Still, I'd rather watch a Leonard Susskind lecture on YouTube than listen to DeGrasse Tyson.

JMHO, if you like it go for it. It won't help you solve your homework problems though.

 

[fresh_42]

Just watched Sabine (et al., e.g. Venus Keus) on a show commenting on current models about the end of the universe.

It was entertaining and what she (they) said was reasonable, i.e. no controversial statements. At least, if you don't mind that multiverses are scientifically irrelevant due to lack of evidence. However, and here comes the fact that it was a tv show, even though on a minor channel late at night and thus only for enthusiasts, it addressed educated people but not exclusively physicists. Therefore it had to remain on a very general level that could not be compared with actual science. And it wasn't meant to be comparable.

 

[phinds]

I just learned recently that Michio Kaku is a bad source to learn physics. I was wondering if the same applies to Tyson. I love the series Cosmos, and was wondering if this series is credible.

My experience is that Kaku used to be a serious physicist but has given up on that and enjoys hearing himself talk, even about stuff he knows nothing about. Tyson is much more well-intentioned and you don't hear him spouting nonsense they way Kaku does but as others have said, pop-sci presentations are NOT education, they are entertainment and will not actually teach you much of anything.

 

[DaveC426913]

Yeah, you don't learn physics from Sagan, Tyson or Kaku, what you do is get inspired by them to go learn physics.

 

[OCR]

At least, if you don't mind that multiverses are scientifically irrelevant due to lack of evidence.

I don't mind at all. . . .

.

 

[BadgerBadger92]

Yeah, you don't learn physics from Sagan, Tyson or Kaku, what you do is get inspired by them to go learn physics.

I mean I’ve learned facts for sure, but I don’t think I understand it concretely.

I think from my studying I understand f=ma and MAYBE time dilation/length contraction vis special relativity and that’s it. Maybe if you didn’t mind I can check with you guys on how it works

 

[phinds]

I mean I’ve learned facts for sure, but I don’t think I understand it concretely.

The problem is that a lot of what they present as "facts" are either badly misleading or just plain wrong and unless you already understand the physics, you can't tell which is which or what they have right.

 

[phinds]

I think from my studying I understand ... MAYBE time dilation/length contraction vis special relativity and that’s it. Maybe if you didn’t mind I can check with you guys on how it works

There are hundreds of threads here on PF about both, and that subject is one on which almost all pop-sci presentations get totally wrong is that they make the statment "time slows down for the traveler" rather than the correct statements that "time APPEARS to slow down for the traveler (but doesn't really)".

 

[BadgerBadger92]

There are hundreds of threads here on PF about both, and that subject is one on which almost all pop-sci presentations get totally wrong is that they make the statment "time slows down for the traveler" rather than the correct statements that "time APPEARS to slow down for the traveler (but doesn't really)".

I think you’ve told me that it only appears to slow down about a year ago.

Other equations I think I understand are velocity, accelerstion, Newtons gravitational force equation, and kinetic energy.

I’m still having troubles with potential energy. I don’t think I really know what it is. I feel like potential energy should be more when you are closer to the earth

 

[hutchphd]

*Yeah, you don't learn physics from Sagan, Tyson or Kaku, what you do is get inspired by them to go learn physics.

As it turns out I did learn physics from Prof Sagan at Cornell (OK it was planetary science but he was the real deal), He was extraordinary.
Tyson is pretty good with the physics and his real job (director of Hayden planertarium) is pretty much public relations which he does extraordinarilly well.
Kaku (IMHO) never says much that is interesting...but I do not know high energy physics

 

[BadgerBadger92]

This is where I’ve been learning most of my physics. That and some Khan Academy. I hope these are good ways to learn physics because they explain it in a way I can understand.

 

[Hornbein]

I just learned recently that Michio Kaku is a bad source to learn physics. I was wondering if the same applies to Tyson. I love the series Cosmos, and was wondering if this series is credible.

I say he's OK. Kaku is a phony.

If you should care to learn quantum physics in a qualitative way, try Richard Feynman's book QED.

 

[BadgerBadger92]

I say he's OK. Kaku is a phony.

If you should care to learn quantum physics in a qualitative way, try Richard Feynman's book QED.

I’m not quite there yet, but I’ll check it out if I remember.

 

[phinds]

I’m still having troubles with potential energy. I don’t think I really know what it is. I feel like potential energy should be more when you are closer to the earth

PE is, to the contrary, in a normal human way of looking at things, greater as you get farther from the surface of the Earth. That makes sense because it takes work to raise something off the surface to a height above the surface. Doing so uses kinetic energy to create potential energy.

But really, PE is frame dependent. If you have an apple 10 feet off the ground and you choose the ground as your reference, then the apple has a certain amount of PE. If you choose the apple's height as your frame of reference, it has no PE. If you choose a point between the apple and the surface, then it has some PE but less than if you choose the surface as the reference.

I am, of course, speaking here of mechanical PE. There are other forms such as electrical PE.

 

[phinds]

This is where I’ve been learning most of my physics. That and some Khan Academy. I hope these are good ways to learn physics because they explain it in a way I can understand.

I skipped around and listened to a few parts of this in the background while I worked on some other stuff. Seems very good to me. Excellent step by step presentations.

 

[hmmm27]

I feel like potential energy should be more when you are closer to the earth

Well, gravity decreases with altitude, but PE still increases.

 

[BadgerBadger92]

Well, gravity decreases with altitude, but PE still increases.

I’m having trouble understanding why it increases as you raise it, because at one point it won’t be attracted towards the earth. Is it a bell curve?

I hope I’m making my question clear enough. I may be confusing PE with gravitational force

 

[Borek]

at one point it won’t be attracted towards the earth

It will be attracted always.

$$F = G_0 \frac {m_1m_2}{r^2}$$

(at least in classical physics, I have no idea whether we know for sure what happens over really vast distances)

 

[weirdoguy]

I’m having trouble understanding why it increases as you raise it,

Potential energy is defined the way that it increases in the direction oposite to the one force is acting (that is why there is a minus sign in the force= - gradient of potential energy). In other words, force points in the direction in which potential energy of this force decreases.

 

[Ibix]

(at least in classical physics, I have no idea whether we know for sure what happens over really vast distances)

Gravity is infinite ranged in GR too. For quantum gravity we'll have to get back to you.

However, if there are multiple gravitating bodies then there are points where gravitational potential stops rising and starts decreasing again. That may be what's confusing @BadgerBadger92 - "gravitational potential increases as you go away from Earth" is only that simple in a universe that's empty except for the Earth, or where you've already determined that the gravitational influence of other bodies is negligible.

 

[BvU]

I’m having trouble understanding why it increases as you raise it, because at one point it won’t be attracted towards the earth. Is it a bell curve?

I hope I’m making my question clear enough. I may be confusing PE with gravitational force

This is exactly why math is so crucial and indispensable in physics: one is the derivative of the other. Once you can 'see through' that, it becomes a lot easier.

##\ ##

 

[Borek]

Gravity is infinite ranged in GR too. For quantum gravity we'll have to get back to you.

What I really mean is that in my - I admit, limited - understanding there are some problems with the "simple" model on the cosmological scale, which we try to deal with introducing some exotic concepts (like dark energy and whatnot). As long as we don't know what is the source of the observed discrepancies there is a slight chance our existing models are somehow limited (won't be the first time, and it doesn't make them in any way "wrong").

I am probably overly careful here.

 

[malawi_glenn]

I’m having trouble understanding why it increases as you raise it, because at one point it won’t be attracted towards the earth. Is it a bell curve?

The gravitational force on an object with mass ##m## due to Earth's gravity is ##F = \dfrac{G\cdot m \cdot m_\text{Earth}}{r^2}## where ##r## is the distance from the centre of the Earth. Note that this formula is valid for ##r \geq r_\text{Earth}## (also assuming spherical Earth). The force of gravity is inversely proportional to the distance squred. If you wanna account for more objects, like the moon and such, you need to write the vector sum of those forces as well.

With a change variables we can write it as ##F = \dfrac{G\cdot m \cdot m_\text{Earth}}{(r_\text{Earth}+h)^2}## where ##h## is the height above the surface of the Earth.

The potential energy for an object at height ##h## is then the work needed to lift that object from the surface of the Earth so that it becomes at rest at that height: ##\displaystyle W = \int_{r_\text{Earth}}^{r_\text{Earth}+h} \dfrac{G\cdot m \cdot m_\text{Earth}}{r^2} \text{d} r##. For very small ##h## though, the force of gravity is almost constant ##F \approx mg## where ##g = \dfrac{G \cdot m_\text{Earth}}{r_\text{Earth}^2} \approx 9.8## m/s². Thus the work for such small heights can be written as ##W = mgh##.

Potential energy can be thought of "work that has not yet been done"

 

[phinds]

I’m still having troubles with potential energy. I don’t think I really know what it is. I feel like potential energy should be more when you are closer to the earth

Well, there's a very simple experiment you can do at home to convince yourself otherwise. Take a 5lb weight and set it gently on your foot. You'll feel a pressure but no pain. Now use your muscles to raise the weight up by three or four feet and then drop it on your foot. After you get out of the emergency room, but before the pain meds have worn off, think about why the two situations had such a different effect.

 

[fresh_42]

Please create a thread in the Classical Physics forum if you further want to discuss potential energy.

This has nothing to do about any physicist like Neil deGrasse Tyson (or others) who are on one hand respected physicist and entertainer on the other hand, who want to bring physics to a broader audience than just university students, and the questions which parts of their work can be considered a serioius reference for actually learning physics.

I think these differences have been sufficiently discussed, so this thread can be closed.