401

Physics, Astronomy & Cosmology / Re: Do we go round in circles?

« on: 18/03/2019 15:59:50 »

Infinity is never a number. If there is ever only one thing you learn about infinity that should be it. What is 5 times infinity? It is undefined in mathematical terms.

Maybe my mind is slipping but "undefined" would be something that is undefined in mathematics, ie 0/0 0^0 can not be defined etc N/0 →∞ is not strictly undefined, in that we know which way the number is headed, if we were to try and calculate the outcome. Although ∞/∞ would be undefined like 0/0 https://en.wikipedia.org/wiki/Undefined_(mathematics)

402

Physics, Astronomy & Cosmology / Re: Do we go round in circles?

« on: 18/03/2019 15:51:25 »

You are preaching to the converted, there, Jeffrey.

2. Infinity is not a number.

Just one of the many times I've said it; usually in response to its being used as though it were a number.

BTW; if you have any comments about the points in #3, I would welcome them.

OK

Infinity is concept of a number that can never be attained ie N/0 →∞. Your number sequence given in 3 is correctly infinite although the number 1.01, 1.001 ultimately → 1.0
"
4. In calculus, a sequence like 1, 2, 3, 4 is considered as "converging to infinity", but is there actually an object "infinity" that this sequence is converging towards?  " It is converging towards the concept of a number that can never be attained.

Infinity is a mathematically conceptual number that can never be attained or written or imagined, except to say it is bigger than anything ever imagined. ie Big

 

403

Physics, Astronomy & Cosmology / Re: What is an "event" ?

« on: 18/03/2019 15:28:31 »

An event is definitely something that happens in a region of space and time,

That's not how the term event is defined. An event is a point in space at an instant in time, i.e. = (t, x, y, z)  is an event.

The inflationary stage preceding the Big Bang was an event, ..

Wrong. Please read the definition of event at
https://en.wikipedia.org/wiki/Event_(relativity)

Correct link https://en.wikipedia.org/wiki/Event_(relativity)

From your link  "an event is the instantaneous physical situation or occurrence associated with a point in spacetime"

From the oxford English dictionary an event in physics is
"
1.3Physics A single occurrence of a process, e.g. the ionization of one atom.

Example sentences
‘The aim of induction is to find series of events whose frequency of occurrence converges toward a limit.’
‘Consider our passage through time as riding the shockwave of the bang event.’
‘In the lower graph the current scale is amplified so that single channel events can be distinguished.’
"
The Big Bang according to the oxford English dictionary was an event

https://en.oxforddictionaries.com/definition/event

404

Physics, Astronomy & Cosmology / Re: What is an "event" ?

« on: 18/03/2019 15:19:52 »

I don't think any cosmologist would refer to the inflationary stage (which followed the big bang) an event.  It is an epoch, which implies a significant period of time.  It is no more an event than is the Holocene epoch which is currently ending.  And while the inflation epoch was certainly of shorter duration than the Holocene, it represented a far greater percentage of the entirety of the history of time while it was going on.

This is of thread, but I may start a thread to discuss this.

According to a couple of speculative theories I have read, the inflationary stage came first and caused virtual particles to become separated and become real particles. A little like Hawking radiation. Further more these particles decayed to become stable particles, giving off lots of heat creating the hot big bang. The concept of Aeons conformal cyclic cosmology by Roger Penrose tends to side step singularities and Big Bangs, but does require inflation as g>0.

Do you have a reference for your comment above. The term Big Bang is term which seems to have evolved since Hoyle coined the phrase and means a lot to different people. In particular I am interested in reference to the time duration of the inflationary stage  ie what do you mean by Significant time

405

Question of the Week / Re: QotW - 08.01.13 - How do Boomerangs Work?

« on: 18/03/2019 14:55:07 »

Does no one use google and wiki?

Not back in 2008 when this question was answered.

Despite Google being founded in 1998, they weren't so totally dominant in search (and advertising) back in 2008.

Despite Wikipedia being founded in 2001, they didn't have the reputation, breadth, depth and editorial standards that have been built up today.

Back then, people would probably have looked up a paper encyclopedia (if they didn't know any university lecturers they could ask)...
- On one occasion, I saw people selling paper encyclopedias in a shopping center. They approached me, but when I asked about the cost of the CDROM version, they totally lost interest. Already they could see that digital media was eating their lunch.

Woops I hadn't noted the date stamp, Colin told me I needed to do some posts so that I could use links.

I do have a friend who claims he made his fortune selling encyclopedias, I suspect he owned the company:)

406

Technology / Re: Is it possible to create a electrostatic / magnetic bubble for breathable air?

« on: 17/03/2019 18:18:51 »

Breathing masks for cyclists already existhttps://www.londoncyclist.co.uk/cycling-masks-and-the-shocking-results/

Electrostatics are already incorporated in many masks, and if you want to import a container load from china you can get a good price https://www.alibaba.com/showroom/electrostatic-filter-for-mask.html.

407

Physics, Astronomy & Cosmology / Re: What is an "event" ?

« on: 17/03/2019 18:09:45 »

I understand that an "event" is used to mean a point on a spacetime coordinate system  or  it can be one element  of  the set of aĺl events (which doesn't help).

But if we take  an event as a physical oçcurence , what can we say about it?...

It is something which has a spatial point location at an instant of time. Events are pretty much fictional in practice on a large scale because real objects are not point objects and have spatial extent. They apply more aptly in particle physics. This does not mean that events don't occur and can't be described on the large scale though. They're approximations in that case like a circle is not exactly what the top of a tuna can is.

An event is definitely something that happens in a region of space and time, and can encompass multiple interactions, as a result of an initial trigger event. The inflationary stage preceding the Big Bang was an event, that covered a period of time whereby particles came into existence, before resulting in a hot big bang and the slowing of the inflationary stage, which is now accelerating as g >0.

I am not so sure a tin of tuna can be described as an event although I suppose they happen to come into existence at a point in space and time, which could be a little chaotic as some have circular lids and others rectangular. The contents may result in different flavours on a galactic scale

408

Famous Scientists, Doctors and Inventors / Re: Who invented the dildo?

« on: 17/03/2019 17:56:06 »

I guess some one just wanted to play around, and were told to keep their fingers out.

Or

Perhaps it has older origins 1500 th century, with witches broomsticks https://hyperallergic.com/332222/first-known-depiction-witch-broomstick/

Or perhaps it started with an enjoyable slip up / accident

sorry I needed 10 posts, the link works now thanks Colin

409

Marine Science / Re: Do sharks only eat live fish?T

« on: 17/03/2019 17:41:02 »

Jon wants to know:

Do sharks only eat live fish? Or could they be more opportunistic, such that a dead fall would provide reason to linger in an area?

Do you know the answer?

Yes they eat dead fish, and if they arent dead when they start eating them, they are when thety are finished

410

Geology, Palaeontology & Archaeology / Re: Can you help me identify a rock?

« on: 17/03/2019 16:55:15 »

Lan wants to know:

Can you help me identify a rock?

We were staying in a hotel next to Udawalawe National Park in Sri Lanka and found lots of rocks that had specks of silvery metallic shiny pieces in them. The majority of the stones had highly shiny silvery specks while some had black specks that were larger but still glisten and catch the light so as to shine. Rocks were in general very dark in colour and very compact, although i think some were sedimentary, as I could see their layers and these layers split easily. Do you know what type of rocks these are?

Can you help figure out the answer?

sounds like you are talking schist of the mica variety. A picture would be useful.

411

Question of the Week / Re: QotW - 08.01.13 - How do Boomerangs Work?

« on: 17/03/2019 16:53:03 »

How does a boomerang work and what is the principle behind that?
Asked by Anand, Colchester                                   

Does no one use google and wiki "
A returning boomerang is a rotating wing. It consists of two or more arms, or wings, connected at an angle; each wing is shaped as an airfoil section. Although it is not a requirement that a boomerang be in its traditional shape, it is usually flat.
Boomerangs can be made for right or left handed throwers. The difference between right and left is subtle, the planform is the same but the leading edges of the aerofoil sections are reversed. A right-handed boomerang makes a counter-clockwise, circular flight to the left while a left-handed boomerange flies clockwise to the right. Most sport boomerangs weigh between 70 to 110 grams (2.5 to 3.9 oz), have a wingspan of 250 to 350 millimetres (9.8 to 13.8 in) and have a range on most is between 20 and 40 m (22 and 44 yd).
"
wiki/Boomerang Its an aerofoil

Sorry for the noddy post, but need nine posts to put in links

412

General Science / Re: Should I worry about electromagnetic fields (EMFs)?

« on: 17/03/2019 16:47:14 »

Don asks:

Should I worry about EMFs from cell phones?

I keep hearing claims that electromagnetic fields from cell phones (in particular fears about 5G), cell towers, "smart" meters and even LED lights are harmful. The harms include "dirty" electricity causing cancer, killing or chasing away birds and wildlife, causing infertility, and so on.  How fearful and how cautious should we really be?

What do you think?

No the EMF field strength from a mobile phone is not something you should worry about, it is in the order of mW. New radars using 3,4,5 G technologies are perfectly safe, however the old radars on ships banging out lots of Watts could make your fillings hurt, if you stood in front of them, and even light fluorescent light tubes. Which I am pretty sure was not good for your health. A good trick with apprentice electricians was to point a radar at a fluorescent light tube and tell them to fix the light switch, with the wires disconnected the tube remained lit. Very funny, but in retrospect possibly dangerous.

413

Physics, Astronomy & Cosmology / Re: Do we go round in circles?

« on: 17/03/2019 16:38:27 »

If you can define a topological space which has the real numbers as a subset, plus an additional object called "infinity", and if the notion of convergence is such that sequences converge to this additional object.  In that sense, infinity exists.  (I don't believe I said that )

Infinity is number that can never be attained, a distance that can never be travelled in an eternity, a time that can never be reached. ie Infinity has no limit it is unending.


Ps it is also useful in maths to simplify equations as f(a value) → ∞ something can be ignored in an equation, making the sums easier.

414

General Science / Re: Are cannabis-infused foods dangerous?

« on: 15/03/2019 09:57:09 »

I am very interested in this matter. But still did not get into something

You might also want to look into the role of dopamine in schizophrenia and parkinsons disease. The medication for one can cause the other.

Cannabis is also used by some people with Parkinsons to alleviate the symptons. Also Cannabis may be a trigger for those developing psychotic problems like schizophrenia.

I can not post links for some reason, but if you google the subject, you will get hits.

415

General Science / Re: Are cannabis-infused foods dangerous?

« on: 13/03/2019 18:07:38 »

Have you ever heard about these foods infused cannabis?

You could always go to Amsterdam and try tasting some of the cookies legally available in the Cafes.

Cannabis may be linked with early onset Schizophrenia, in those that are likely to develop the illness. I dont appear to be able to post external links, for some reason, but if you want more info you can google it.
If your one of your parents have schizophrenia, it is not a good idea to take cannabis.