Hatrack River Forum: I'm reading Hawking (A Question)

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Posted by T_Smith (Member # 3734) on :

I've been reading Hawking's Brief History of Time, and have been enjoying it very much. I tried to start with Einstien and went crosseyed before page 6; needless to say, Hawking has been a lot easier to read thus far. I have a tendency to read something, continue on, and then when I'm not doing anything, I think about things.

Well one of the things my mind jumped to was something Hawking wrote in the second chapter, which was that by the equation E = mc^2, the energy a object has due to it's motion will add to it's mass.

Over the years of just about any science class I ever slept through in high school, biology included, I came to believe that mass was a measure of matter, and something that was repeated every other day "matter/energy can not be created or destroyed, but can be changed."

So I'm confused now. If something is sped up, it then takes up more space? Or what?

Posted by EarlNMeyer-Flask (Member # 1546) on :

In physics, the mass of an object is defined as a measure of the difficulty of accelerating the object. An object going faster will have more mass, meaning that increasing its speed will be harder.

In biology, saying that mass is a measure of matter is imprecise. It's really our physical world intuition of the physics concept of mass.

Thus, the law of thermodynamics is maintained, and there is no creation of new matter or energy.

I'm not certain about whether or not an object accelerated near to the speed of light will take up more space. (Even if there is no new matter created, the existing matter could be more spread out). There is a phenomena that I think has been measured called length contraction that finds that objects compress a very small amount when accelerated. Thus, an accelerated object should actually be contained in less space.

However, this presumes that we know what space is, and that it doesn't change much (whatever it is) when objects are accelerated.

Posted by T_Smith (Member # 3734) on :

Ok, so if mass is the measure of the difficulty of accelerating the object, then yeah, it makes sense. It's going to take more energy to move an object faster. Ok, that makes sense. It then explains that an object can not go faster than the speed of light, because then it's mass would be infinite, and impossible to accelerate any faster.

Ok, makes sense. If mass is all about the difficulty in moving something, it's simple to know. How then did I come to think that mass has to do with matter and space thats filled? This probably explains why I got a B- in most science classes.

Posted by EarlNMeyer-Flask (Member # 1546) on :

Your first notion of mass is what is usually presented as our common-sense/intution of mass, and it is what it is usually defined as in at least lower biology course textbooks.

Posted by Mike (Member # 55) on :

Interestingly enough, most of the mass in ordinary matter is due to the energy of all the little sub-atomic particles whizzing around each other. So, mass isn't just what makes things hard to accelerate. It is also what makes things attract each other through gravity.

Edit: and a bit about the Lorentz Contraction.

Posted by Telperion the Silver (Member # 6074) on :

You're so cute T_Smith. [Smile]

Posted by Morbo (Member # 5309) on :

Nate, here's a link that might blow your mind: Mach's Principle as put forth by Einstein.

Good luck, I only understand about 40% of it. [Evil Laugh]

Posted by Nell Gwyn (Member # 8291) on :

I read A Brief History of Time a few years ago (also as a non-scientist), and I really enjoyed it as well. But it definitely gave me several headaches! [Wall Bash]

Posted by Morbo (Member # 5309) on :

Another factoid: Hawking was told that every additional equation would reduce his readership by a huge amount.
So he only included 2-3 equations in his book...

Posted by DarkKnight (Member # 7536) on :

I think he only included one equation in a Brief History of Time?

Posted by Kwea (Member # 2199) on :

quote:
Originally posted by Morbo:
Another factoid: Hawking was told that every additional equation would reduce his readership by a huge amount.
So he only included 2-3 equations in his book...

And it is one of the best selling pure science books...

Ever.

Go figure. [Wink]

Posted by Dan_raven (Member # 3383) on :

Compared to Romance novels wich are 100% formula.

Posted by John Van Pelt (Member # 5767) on :

So if M is the measure of mass readership, and E is the number of equations, then C would be the cerebral appetite of the book buying public, such that:

M = E^(-2C)

Posted by Ben (Member # 6117) on :

I may be mistaken, but i think your wife bought her first copy of that book at our 7th grade scholastic bookfair.

its sad if i remember that correctly.

Posted by mackillian (Member # 586) on :

It is, in fact, that very copy.

Posted by Ben (Member # 6117) on :

so...very...sad...

Posted by Teshi (Member # 5024) on :

I love A Brief History of Time! It lives on my bedside table.

[Big Grin]

Posted by Destineer (Member # 821) on :

Morbo, what's gotten you interested in Mach's Principle?

That was one of the topics of my undergraduate thesis in the philosophy of physics.

Posted by John Van Pelt (Member # 5767) on :

quote:
Originally posted by Teshi:
I love A Brief History of Time! It lives on my bedside table.

Me too! Mine too! [Smile]

quote:
Originally posted by Dan_raven:
Compared to Romance novels wich are 100% formula.

I mentioned this to Sharpie, and she said it just proves the phenomenon is more complicated than we thought -- perhaps a disjoint parabola -- or perhaps it is not the number of equations, but the proportion that is formulas. From 1 to 500 equations, readership drops from 10 million to 20, but at 100% formula it goes back up to 10 million....

[Cool]

Ha, ha, way to kill a joke, jvp

Posted by etphonehome (Member # 999) on :

I remember reading A Brief History of Time the summer before my freshman year of high school, and I really enjoyed it. I want to re-read it someday, but I have a mile-long list of books I've never read that I want to get through first.

Posted by 0range7Penguin (Member # 7337) on :

I was just reading the new Wheel of Time book that just came out so the first thing i though of when i saw this topic was Arthur Hawking? What can u read of his?

Then I reallized who it was actually talking about....