The Naked Scientists
  • Login
  • Register
  • Podcasts
      • The Naked Scientists
      • eLife
      • Naked Genetics
      • Naked Astronomy
      • In short
      • Naked Neuroscience
      • Ask! The Naked Scientists
      • Question of the Week
      • Archive
      • Video
      • SUBSCRIBE to our Podcasts
  • Articles
      • Science News
      • Features
      • Interviews
      • Answers to Science Questions
  • Get Naked
      • Donate
      • Do an Experiment
      • Science Forum
      • Ask a Question
  • About
      • Meet the team
      • Our Sponsors
      • Site Map
      • Contact us

User menu

  • Login
  • Register
  • Home
  • Help
  • Search
  • Tags
  • Recent Topics
  • Login
  • Register
  1. Naked Science Forum
  2. Non Life Sciences
  3. Physics, Astronomy & Cosmology
  4. how do objects heat up in a vacuum? aka black holes
« previous next »
  • Print
Pages: [1]   Go Down

how do objects heat up in a vacuum? aka black holes

  • 7 Replies
  • 4189 Views
  • 0 Tags

0 Members and 1 Guest are viewing this topic.

Offline yor_on (OP)

  • Naked Science Forum GOD!
  • *******
  • 81550
  • Activity:
    100%
  • Thanked: 178 times
  • (Ah, yes:) *a table is always good to hide under*
how do objects heat up in a vacuum? aka black holes
« on: 09/01/2019 12:02:50 »
Read this " http://curious.astro.cornell.edu/disclaimer/86-the-universe/black-holes-and-quasars/general-questions/436-what-type-of-energy-does-a-black-hole-have-intermediate " where it is stated that "  These objects can gain energy from the black hole, as they fall into the potential well they heat up and radiate (often in the X-ray region of the spectrum). " ?

that they do it falling from space here on Earth is due to friction, but a mass following a geodesic in a vacuum?
Why would they 'heat up'?
Tidal forces?

Can't  be the Unruh effect
Logged
URGENT:  Naked Scientists website is under threat.    https://www.thenakedscientists.com/sos-cambridge-university-killing-dr-chris

"BOMB DISPOSAL EXPERT. If you see me running, try to keep up."
 



Offline Kryptid

  • Global Moderator
  • Naked Science Forum King!
  • ********
  • 8082
  • Activity:
    1.5%
  • Thanked: 514 times
Re: how do objects heat up in a vacuum? aka black holes
« Reply #1 on: 09/01/2019 16:39:35 »
I assume they are talking about an accretion disk, which does indeed radiate heat due to friction: https://en.wikipedia.org/wiki/Accretion_disk
Logged
 

Offline chiralSPO

  • Global Moderator
  • Naked Science Forum King!
  • ********
  • 3743
  • Activity:
    0%
  • Thanked: 531 times
Re: how do objects heat up in a vacuum? aka black holes
« Reply #2 on: 09/01/2019 16:53:26 »
My understanding is that the intense heat generated in accretion disks is due to collisions between particles with drastically different relative velocities. 

EDIT: Oops! Crossed with Kryptid!
Logged
 

guest47899

  • Guest
Re: how do objects heat up in a vacuum? aka black holes
« Reply #3 on: 09/01/2019 23:51:31 »
black holes have zero entropy. zero entropy is at absolute zero or sub absolute zero. sub absolute zero can produces extreme temperatures that exceed any positive above absolute zero temperatures.
Logged
 

Offline Kryptid

  • Global Moderator
  • Naked Science Forum King!
  • ********
  • 8082
  • Activity:
    1.5%
  • Thanked: 514 times
Re: how do objects heat up in a vacuum? aka black holes
« Reply #4 on: 10/01/2019 00:55:18 »
Quote from: Pesq on 09/01/2019 23:51:31
black holes have zero entropy.

Black holes have finite entropy. The larger the black hole, the larger the entropy (it's linearly proportional to the surface area of the event horizon).
Logged
 



Offline chiralSPO

  • Global Moderator
  • Naked Science Forum King!
  • ********
  • 3743
  • Activity:
    0%
  • Thanked: 531 times
Re: how do objects heat up in a vacuum? aka black holes
« Reply #5 on: 10/01/2019 02:04:44 »
Quote from: Pesq on 09/01/2019 23:51:31
zero entropy is at absolute zero or sub absolute zero.
Not quite. If we consider a system with fixed volume and fixed number of particles, then temperature is inversely proportional to the rate of change of entropy with respect to the rate of change of internal energy.
  T = 1/(∂S/∂U)

What this means is: iff (iff means if and only if) the temperature is positive, then entropy increases as the energy of the system increases, whereas iff the temperature is negative, then entropy decreases as the energy of the system increases. Lasers are a common example of systems in which the temperature is negative--as you put energy into the laser, it becomes more ordered, and then becomes less ordered when discharged.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/temper2.html
Logged
 

Offline yor_on (OP)

  • Naked Science Forum GOD!
  • *******
  • 81550
  • Activity:
    100%
  • Thanked: 178 times
  • (Ah, yes:) *a table is always good to hide under*
Re: how do objects heat up in a vacuum? aka black holes
« Reply #6 on: 10/01/2019 06:07:10 »
Ahh

Ok, that one ,made sense, at last :)
Thanks Kryptid and Chiral
Logged
URGENT:  Naked Scientists website is under threat.    https://www.thenakedscientists.com/sos-cambridge-university-killing-dr-chris

"BOMB DISPOSAL EXPERT. If you see me running, try to keep up."
 

Offline Bored chemist

  • Naked Science Forum GOD!
  • *******
  • 31101
  • Activity:
    13%
  • Thanked: 1291 times
Re: how do objects heat up in a vacuum? aka black holes
« Reply #7 on: 10/01/2019 11:00:59 »
Quote from: Pesq on 09/01/2019 23:51:31
sub absolute zero.
That's a term which needs a careful definition.
Also, plenty of materials are not perfectly ordered in the crystalline state. Frozen carbon monoxide has the molecules aligned randomly for example.
So it does not have zero entropy at zero kelvin.
Logged
Please disregard all previous signatures.
 



  • Print
Pages: [1]   Go Up
« previous next »
Tags:
 
There was an error while thanking
Thanking...
  • SMF 2.0.15 | SMF © 2017, Simple Machines
    Privacy Policy
    SMFAds for Free Forums
  • Naked Science Forum ©

Page created in 0.406 seconds with 43 queries.

  • Podcasts
  • Articles
  • Get Naked
  • About
  • Contact us
  • Advertise
  • Privacy Policy
  • Subscribe to newsletter
  • We love feedback

Follow us

cambridge_logo_footer.png

©The Naked Scientists® 2000–2017 | The Naked Scientists® and Naked Science® are registered trademarks created by Dr Chris Smith. Information presented on this website is the opinion of the individual contributors and does not reflect the general views of the administrators, editors, moderators, sponsors, Cambridge University or the public at large.