It is currently Tue Oct 15, 2019 4:25 am


Post new topic Reply to topic  [ 10 posts ] 
Author Message
 Post subject: Fact or inference? ..
PostPosted: Thu Dec 30, 2010 10:24 am 
Offline

Joined: Mon Jan 09, 2006 11:05 am
Posts: 5271
Location: Lancashire
In popular astronomy literature, we see references to dark energy, dark matter, antimatter and virtual particles, etc. These phenomena are often presented in such a matter-of-fact way as to imply to the lay person that they actually exist, but do they?
I'm a lay person on these matters, but I happen to have a German son-in-law with a doctorate in quantum mechanics. Over the holiday period he came over to England and cleared up some misconceptions.
He assured me that there's no concrete evidence yet for the existence of virtual particles and antimatter. These supposed phenomena are inferences from previous data. At this point in time, they exist only as formulae. The same goes for dark matter and dark energy, and even black holes - nobody has seen a black hole directly, despite strong circumstantial evidence.
It goes to show that we should be cautious about some of the claims made by journalistic science writers. :wink:

_________________
brian


Top
 Profile Send private message  
 
PostPosted: Thu Dec 30, 2010 11:26 am 
Offline
Site Admin

Joined: Fri Dec 03, 2004 11:24 am
Posts: 4375
Location: Greenwich, London
brian livesey wrote:
He assured me that there's no concrete evidence yet for the existence of virtual particles and antimatter.

I read a little while ago that anti-matter had been isolated and trapped.

http://www.bbc.co.uk/news/science-environment-11773791

Does that mean that it exists?

"Dark" means unknown and, yes, black holes are inferred but most scientists in the field are confident that they exist given the evidence. I see no problems really. I read articles by sceptics and supporters alike but I suppose it pays to remind ourselves that we need to be careful about what is factual and what is inferred.

_________________
200mm Newtonian, OMC140, ETX90, 15x70 Binoculars.


Top
 Profile Send private message  
 
PostPosted: Thu Dec 30, 2010 8:30 pm 
Offline

Joined: Fri Jul 06, 2007 9:51 pm
Posts: 349
brian livesey wrote:
I happen to have a German son-in-law with a doctorate in quantum mechanics......He assured me that there's no concrete evidence yet for the existence of virtual particles and antimatter.


Antimatter has been seen to exist since the 1930's in the case of the positron, the evidence for this is as concrete as that for the electron.

"Virtual particles" by definition can never exist, if they do then they will no longer be "virtual" but will be "real particles".


Top
 Profile Send private message  
 
 Post subject:
PostPosted: Fri Dec 31, 2010 11:57 am 
Offline

Joined: Mon Jan 09, 2006 11:05 am
Posts: 5271
Location: Lancashire
You mentioned the positron as an example of antimatter. Some years ago, I had a full body scan at the local hospital and asked the technician operating the machine what type of radiation was used. He said: "Antimatter". He then qualified this by saying that the radiation was positrons.
My physicist son-in-law told me that positrons are not antimatter.

_________________
brian


Top
 Profile Send private message  
 
 Post subject:
PostPosted: Fri Dec 31, 2010 2:10 pm 
Offline
Site Admin

Joined: Fri Dec 03, 2004 11:24 am
Posts: 4375
Location: Greenwich, London
If you read that BBC report I linked it says that scientists produced and trapped whole anti-hydrogen atoms.

_________________
200mm Newtonian, OMC140, ETX90, 15x70 Binoculars.


Top
 Profile Send private message  
 
 Post subject:
PostPosted: Tue Jan 04, 2011 12:25 am 
Offline

Joined: Sat Dec 11, 2004 8:18 pm
Posts: 6501
Location: Manchester
Dear Brian, Joe and Big Kev,
Speaking personally from a lay-man amateur astronomer stance I think I can say I'm probably as sceptical as most about many aspects of current cosmology eg far from completely happy about dark energy and dark matter. Indeed if anything I think I'm happier with MOND or similar possible theories.
I also attended an interesting talk a few months back by a young cosmologist (not quite finished her PhD yet), who I was pleased to hear quite openly sceptical about "Hawking's Radiation" and felt pretty sure if it does actually exist it would be probably un-observable being very very weak.
However, that said, I must confess that even I feel reasonable happy about Black Holes. Even though BHs have not been seen directly, I think the fairly recently observed\imaged stars rapidly orbitting the "nothing" at the centre of our Milky Way seen are indicative of there being a Supermasive BH there. If I heard correctly they've even tracked one or two stars round a complete very small orbit.
So I think I accept that something as yet still un-observed very massive probably exists at the centre of the Milky Way and that something is probably\possibly a Black Hole.
Best wishes from Cliff
PS - What am I saying - me possibly believing cosmologists, I cann't believe it.


Top
 Profile Send private message  
 
 Post subject:
PostPosted: Tue Jan 04, 2011 10:48 am 
Offline

Joined: Mon Jan 09, 2006 11:05 am
Posts: 5271
Location: Lancashire
Regarding the BBC report Joe. Producing "antimatter" at CERN isn't the same as saying that antimatter exists in nature. There are, as you know, human-made "elements" that last for only a moment.

_________________
brian


Last edited by brian livesey on Thu Jan 27, 2011 9:36 am, edited 1 time in total.

Top
 Profile Send private message  
 
 Post subject:
PostPosted: Fri Jan 07, 2011 12:48 am 
Offline

Joined: Sat Dec 11, 2004 8:18 pm
Posts: 6501
Location: Manchester
Dear Brian et al
In my simple minded way I cann't help wondering if the very short lived new elements really existed at all or happened to be someting that conveniently (or possibly inconveniently) apparently produced very brief observable characteristics suggesting them to be some sort of new element ?
As for Black Holes, as I said before, I must admit, I'm now pretty well sold on their reality now, even though they haven't been observed directly.
Furthermore (assuming they do really exist ?) I am happy to believe Black Holes may never be proved to existby "ordinary" direct observation. As far as I'm concerned, the apparently actual observations of stars orbitting in small orbits at fantastically fast speeds around a "nothing" at the middle of the Milky Way is pretty well good enough for me.
However, as for Hawking Radiation and Evaporating Black Holes - yes and no! I treat them as mathematical possibilities.
Best wishes from Cliff


Top
 Profile Send private message  
 
 Post subject:
PostPosted: Sun Jan 09, 2011 9:29 pm 
Offline

Joined: Sun Aug 13, 2006 12:29 pm
Posts: 663
Location: Goosnargh, north of Preston, UK
brian livesey wrote:
Some years ago, I had a full body scan at the local hospital and asked the technician operating the machine what type of radiation was used. He said: "Antimatter". He then qualified this by saying that the radiation was positrons.


Hi Brian,

I didn't know anything about full-body scans prior to reading this thread, but I assume you had a Positron Emission Tomography (PET) scan. Having read up on it, the technology is just astonishing. It's off-topic for this forum, so I won't go on about it, but invite anyone interested to read the wikipedia entry.

http://en.wikipedia.org/wiki/Positron_emission_tomography

As a result of the annihilation of positrons and electrons, in your body, your body was emitting 511 keV gamma ray photons, in pairs, each photon travelling in opposite directions. Quite amazing.

_________________
David Entwistle


Top
 Profile Send private message  
 
 Post subject:
PostPosted: Mon Jan 10, 2011 10:31 am 
Offline

Joined: Mon Jan 09, 2006 11:05 am
Posts: 5271
Location: Lancashire
So that's why I glow at night! :wink:

_________________
brian


Top
 Profile Send private message  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 10 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group