Because there is lots more independently repeatable measurable observations available to do in a lab, than from earth or satellite based instruments. Its possible to measure lots of observations about the moon from earth, like reflectivity, or elevation mapping, but not everything, stuff like analyzing soil composition is better done in a lab.
Black Hole Lecture at Stanford, April 2nd
- Thread starter JeffKeryk
- Start date
They collected physical evidence, you can dance around it all you want. That's what the term "physical" means.
Just like with Mars, we speculated there might've been water on it from the observational evidence, but we sent multiple robots there to collect the physical evidence.
MolaKule
Staff member
I believe that image was captured with the Chandra X-ray telescope; anything else is usually a simulation or an artist rendering, and even then, much is "inferred" about Black Holes.
Stephen Hawking had a chapter in "Quantum Gravity, " an Oxford Symposium (1975), on '"Particle Creation in Black Holes," a very interesting but theoretic read.
As Astro14 stated, even Black Holes radiates energy across the spectrum and in doing so, loses energy so they must eventually die.
Addendum: "Classical black holes are defined by the property that things can go in, but don’t come out. However, Stephen Hawking calculated that black holes actually radiate quantum mechanical particles. The two important ingredients that result in back hole evaporation are (1) the spacetime geometry, in particular the black hole horizon, and (2) the fact that the notion of a “particle” is not an invariant concept in quantum field theory Stephen Hawking published his paper “Particle Creation by Black Holes”[1] in 1975. In this article, Hawking demonstrated that classical black holes radiate a thermal flux of quantum particles, and hence can be expected to evaporate away. This result was contrary to everything that was known about black holes and classical matter, and was quite startling to the physics community. However, the effect has now been computed in a number of ways and is considered an important clue in the search for a theory of quantum gravity. Any theory of quantum gravity that is proposed must predict blackhole evaporation."
An Introduction to Black Hole Evaporation
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The matter isn't "gone" - it still has mass, which is added to the mass of the singularity, but it is no longer interacting with the rest of the universe outside the event horizon. Whatever that matter was - it is not that anymore - most likely. It's hard to know exactly what is going on inside - but since we cannot know - the question simply becomes pointless.
When a black hole "evaporates" via Hawking radiation - there are new particles formed just outside the event horizon. Because they are new, nothing of the matter that was accreted by the singularity will be returned. Not the form, shape, or function. That matter is basically gone.
Hawking radiation, by the way, is a brilliant deduction by Stephen Hawking. Quantum mechanics predicts that particles and their anti-particle (for example, electron and positron) can randomly form and annihilate each other, without violation of energy conservation, or any other principle of thermodynamics. So Hawking's brilliance was to ponder - what if they formed right on the edge of of a black hole, and one fell in, while the other escaped? So, the escaping particle would now be subtracting from the mass of the black hole and particle by particle, a black hole could evaporate over time, if it were not adding more matter.
This is the likely fate of primordial black holes, which are likely tiny. Only from perturbations in the formation of the universe would we get tiny black holes, because the rest are formed either by the death of a star in a supernova, or by the hundreds of millions of stars in the center of a galaxy, and as a result, are pretty big.
MolaKule
Staff member
Black Holes and the CMB:
Possible New Effects in Black Hole Physics
Possible New Effects in Black Hole Physics
Possible New Effects in Black Hole Physics
www.academia.edu
MolaKule
Staff member
I believe that the proper sizing and placement of airfoils can allow planes to fly.
I believe that certain base oils and additive combinations can result in friction reduction in machine assemblies.
Therefore, I have faith in flying from point A to B (and have done so with proof) and faith that certain formulations provide friction reduction (and have done so with proof).
Furthermore, I would not have been engaged in either of those sciences had I not believed that they work within certain limits and had I not had faith in those scientific results.
I prefer this general definition: "Science is a systematic methodology for investigating natural phenomena."
Definitions allow us to communicate effectively. Faith is often defined in religious terms or as complete trust in something.
When I posted, "You might define faith as something you believe in but cannot prove..." I was referring to persons telling me something that there is no way of proving, but used as proof to their own opinion. I kinda struggle with that because I believe I just may learn something if I am willing to open my mind just a little bit; to perhaps challenge my most deeply held beliefs. Tara Westover wrote something like this in "Educated".
It might be fair to say the 2 definitions of science are very similar. I like mine because I believe nature is ever changing and so the search (investigating) is endless. Just like education. It would be horrible to know everything.
I hope you were able to watch the Youtube video of Professor Blundell's lecture. Unfortunately the video could not capture the professor and the PowerPoint slides at the same time; her presence was so captivating. We were in the presence of greatness.
MolaKule
Staff member
A more readable summary and history of the Black Hole in a less theoretical format:
