Ask a physicist anything. (2)

[Wiccan_Child]

WC. I have a question for you:

Gravity. Why?

Got any interesting hypotheses?

Short answer: Why not?

Long answer: As far as we can tell, space is warped by mass, creating gravity. The question then becomes: what is 'mass', and why does it warp spacetime?
According to the standard model, the Higgs Boson is preferentially attracted to certain particles, slowing them down from lightspeed and giving rise to the illusion of 'mass'. This interaction could be linked to why spacetime is warped around massive particles, though this is just wild conjecture.

 

[PhilosophicalBluster]

How can spacetime be warped? Does that assume that it is made up of particles? Otherwise, what exactly is being pulled by attraction to mass?

-------

And on a semi-related note, I just realized this:

In the formula for force of gravity:
F = G * (mI * mII)/d^2

When the distance between the two centers of the masses is zero, force is undefined. Is this why two particles cannot occupy the same place at once? Or is this just a coincidence? Or am I just overestimating the power of maths?

 

[Wiccan_Child]

How can spacetime be warped? Does that assume that it is made up of particles? Otherwise, what exactly is being pulled by attraction to mass?

It's a continuum in which particles are suspended. The exact nature of spacetime is a mystery, but as science progresses, we're working out more about it. We know it's warped by gravity, and that it's intimately linked to time. Truth is, we just don't know.

-------

And on a semi-related note, I just realized this:

In the formula for force of gravity:
F = G * (mI * mII)/d^2

When the distance between the two centers of the masses is zero, force is undefined. Is this why two particles cannot occupy the same place at once? Or is this just a coincidence? Or am I just overestimating the power of maths?

The formula says that, as the distance between two objects tends to zero, the force of gravity tends to infinity. Eventually, they two objects are so close that the force of gravity overcomes any other repulsive force possible. When this happens, the objects become a black hole. What happens next depends on which theory you subscribe to.

 

[Cabal]

It's a continuum in which particles are suspended. The exact nature of spacetime is a mystery, but as science progresses, we're working out more about it. We know it's warped by gravity, and that it's intimately linked to time. Truth is, we just don't know.

To be fair, there's talk space and time could be quantised, but I'm not sure what theory that fall under (string theory, maybe)?

 

[Cabal]

So some of you may know the lowest order of magnitude with an SI prefix is yocto-, so 1 yoctosecond (ys) = 10^-24 s.

I was at a lecture yesterday and the lecturer said there was talk of making the next five prefices chico-, harpo-, groucho-, gummo-, and zeppo-.

Let it be known that I approve of this.

Also:

dx/dt = velocity
d2x/dt2= acceleration
d3x/dt3 = jerk
d4x/dt4 = snap
d5x/dt5 = crackle
d6x/dt6 = pop.

 

[pgp_protector]

How large would the universe be if their was a Grahm's number of atoms in it

 

[Wiccan_Child]

How large would the universe be if their was a Grahm's number of atoms in it

Big enough that yet another form of notation would have to be invented!

 

[Wiccan_Child]

To be fair, there's talk space and time could be quantised, but I'm not sure what theory that fall under (string theory, maybe)?

Well, there's the Plank length and the Plank time, which, if memory serves, are meant to be the 'graininess' of spacetime. Blows my mind.

 

[pgp_protector]

Big enough that yet another form of notation would have to be invented!

Ok what would happen if we put Grahm's number of atoms in this universe
(Keeping the volume the same)

 

[Cabal]

Panel 3 FTW:

 

[Wiccan_Child]

Ok what would happen if we put Grahm's number of atoms in this universe
(Keeping the volume the same)

A super-duper-massively-massive black hole would suck us all into oblivion! Mwahahahahahaaaaaaa

 

[Cabal]

How about a strong combination of both? What if I have excellent pseudo-scientific proof that the Royal Family are reptillian aliens?

Mr Icke, you've got to stop attention-seeking on internet message boards, it's getting really out of hand!

 

[Cabal]

Ok, I just watched Primer.

Can anyone explain to me what just happened?

"No" is an acceptable answer.

 

[Wiccan_Child]

Ok, I just watched Primer.

Can anyone explain to me what just happened?

"No" is an acceptable answer.

I started watching that, but I got a bit lost half-way through. Wikipedia, as ever, has a delicious summary of how time-travel works.

 

[Chesterton]

I saw Primer. Whew, I'm glad it's not just me. I liked the realism they went for, but once they started using the machine I couldn't make heads or tails of what they were doing.

BTW there was a sequel to this movie...released six hours before this one.

 

[Doveaman]

"Ask a physicist anything". Go through the other thread, you'll get an idea about what it was like. That's what the topic is.

Sure you can. But this is not the place to debate royalism or pseudo-science.

To a degree, though not so much that it dominates the thread. Something that big warrants its own thread.

No. I've seen you post something about gravitational lensing elsewhere, and I thought it'd make a nice post in this thread.

Got it.

 

[Doveaman]

Truth is, we just don't know.

Now you are starting to make sense. I always knew you were a smart guy.

 

[Doveaman]

I asked this question on another thread:

Note too that scientists talk in terms of theory and probabilities not 'facts" or knowing things.

Then why do they present their theories as if they know the facts. Why say "The universe was formed from a Big Bang", a matter of fact statement that can be misleading? Why not say "We think the universe was formed from a Big Bang", a probability statement?

 

[sandwiches]

I asked this question on another thread:
Then why do they present their theories as if they know the facts. Why say "The universe was formed from a Big Bang", a matter of fact statement that can be misleading? Why not say "We think the universe was formed from a Big Bang", a probability statement?

And I'll give you the same answer from that thread:

Weird... The first five links regarding the The Big Bang Theory (not the TV show,) after searching for it on Google show wording such as this:

Big Bang - Wikipedia, the free encyclopedia
"The Big Bang is the cosmological model of the initial conditions and subsequent development of the Universe that is supported by the most comprehensive and accurate explanations from current scientific evidence and observation."

Big Bang Theory
"The Big Bang theory is an effort to explain what happened at the very beginning of our universe."

THE BIG BANG
"Although in this short chapter it will be impossible to tackle all of the questions concerning the creation of everything we know as reality, an attempt will be made to address certain fundamental questions of our being.It will be important to keep in mind that all of this information is constantly being questioned and reevaluated in order to understand the universe more clearly."

WMAP Big Bang Theory
"The Big Bang Model is a broadly accepted theory for the origin and evolution of our universe."

Creation of a Cosmology: Big Bang Theory
"According to the prevailing cosmological models that explain our universe, an ineffable explosion, trillions of degrees in temperature on any measurement scale, that was infinitely dense, created not only fundamental subatomic particles and thus matter and energy but space and time itself. Cosmology theorists combined with the observations of their astronomy colleagues have been able to reconstruct the primordial chronology of events known as the big bang."

So, my question is: Why are you stating as fact what is obviously false?

 

[Wiccan_Child]

Ah, now that is a question .

I asked this question on another thread:
Then why do they present their theories as if they know the facts. Why say "The universe was formed from a Big Bang", a matter of fact statement? Why not say "We think the universe was formed from a Big Bang", a probability statement?

It's to do with the nuance between scientific and colloquial nomenclature, with simplifying established scientific knowledge for the layman, and even slips of the tongue.

First, a 'fact' in science is used more loosely than in strict epistemology: a fact is any established truth. In epistemology, it's anything which is strictly known to be true with 100% certainty; in science, it's known to very high (but not necessarily 100%) certainty.
The existence of atoms is a scientific fact: the evidence for their existence is so overwhelming that they've been proven to exist beyond all reasonable doubt. They aren't know to exist with 100% certainty, so they're not an epistemological fact, but they are a scientific fact.
The difference is similar to that between 'theory' in science and in the public eye; the former considers a theory to be a well-evidenced explanation, while the latter generally consider it to be just a guess.

Second, it is impractical to preface everything with "The evidence suggests", or "We think", or "We conjecture", or "We hypothesis", etc, and it also erodes the public's confidence in science. One need only to look to the USA to see how dangerous that erosion can be.

Third, some scientists (especially those talking outside their field) genuinely make mistakes. A biologist may say that the Big Bang theory "proves the universe began 13.5 billion years ago", despite that being false.