Astrophysicist’s Phrasebook

March 14th is an interesting day. The birthday of Albert Einstein, it’s known to some as Pi Day (courtesy of the US calendar system, making the day 3.14). More comically though, March 14th is International Talk Like a Physicist Day.

However, irrespective of what day it is, if ever you find yourself at a social event with any physics bods, here’s a quick guide to some of the lingo. As a bonus, this is a revised version especially for astrophysicists.

Try using a few of these easy phrases in casual conversation. Your friends will find it hilarious and want to buy you drinks!

Something isn’t strange. It’s anomalous.
– There’s some anomalous van parked outside.

Something isn’t unusual. It’s atypical.
– The seminar’s on a Tuesday this week? Huh. That’s atypical.

Beyond the scope of…
Don’t feel like dealing with a nagging problem? This is your perfect get-out clause.
– Yeah, sure the kitchen could use some cleaning, but I’m afraid that’s beyond the scope of my housework duties.

for Certain values of
a.k.a. how to disagree while appearing to still agree.
(see also for Very small values of).
– Yes, that’s very interesting… for certain values of ‘interesting’.

Use in place of “standard” or “usual”.
– Coffee is my canonical morning drink.

Column Density
Used to refer to how many obstacles are between you and whatever you’re looking at.
– I think I’ll wait a few minutes before buying my next drink. There’s rather a high column density of people between me and the bar right now.

– Look, let’s just see how it goes and deal with any complexities as they happen.

Dark …
Use as a prefix for anything you’re not sure about, or can’t find.
– I’ve searched my hard drive and can’t find it. I guess it must be a dark pdf.

When you’re not sure of the source of something.
– Those two are always together. I sometimes have trouble deblending who said what.
– Can you speak up a bit? It’s too noisy in here, I’m having trouble deblending what you’re saying.

Working out the constituent components of something.
– What’s in this cocktail anyway? I’m having a hard time deconvolving it.

(See Some Discrepancy).

Down in the Noise
Something which can easily be overlooked (on purpose or otherwise).
– “Don’t forget to include the cost of napkins” “Nah, that’s somewhere down in the noise.”

Empirical Data
Anything from personal experience or observation is “based on empirical data”.
– Based on empirical data, I wouldn’t ask her to lunch again.

Use to refer to time. Vaguely.
– Don’t worry, I’ll finish the work. Just maybe not this epoch.

A reasonably educated guess.
– I’d extrapolate that he’s hung over and he’s not coming in this morning.

First-Order Approximation
1. May be used to replace “about”.
– Yeah, my desk is tidy to a first-order approximation.
2. Can also have derogatory usage.
– This is only a first-order approximation to a cup of coffee!

Ground State
It’s not laziness. It’s your ground state.
– Man, I can’t seem to get out of my ground state this morning.

Ideal Case
You’re not ignoring details. You’re referring to the ideal case.
– Of course there’s time for another beer. It’s only 10:45, and in an ideal case they shouldn’t ask us to leave until quarter past 11.

When talking about the consequences of something. Possibly your actions.
– This beer has implications for tomorrow morning

Anything really small.
(Note: if it’s virtually nothing, “negligible” can be replaced by “infinitessimal”)
– My motivation is negligible right now.

It isn’t complicated. It’s non-linear.
– How to get to the cafeteria? Well, it’s a bit non-linear…
Can also be used to describe a person giving a disproportionate reaction to something.
– Dude, all I did was ask when he’d be finished reducing the data, and he went totally non-linear!

It isn’t difficult. It’s non-trivial.
– Organise the party? Oh man… This is going to be non-trivial.

Optical Depth
(See Column Density).

Orders of magnitude
Used to refer to large differences.
(See also Within an order of magnitude).
– I’m still an order of magnitude away from finishing this book.

Use for things which are mutually exclusive, or can’t coincide.
– I know he’s been in the office, but I haven’t seen him all week. Our schedules must be orthogonal at the moment.

Don’t refer to light. Refer to photons.
– It’s getting dark in here. I need more photons.

Photon flux
(As with photons).
– Could you open the blinds? I need a higher photon flux to read by.

Prototypical example
The first of something.
– I thought I’d make pancakes again. The prototypical example from last Tuesday was pretty good!

Potential Well
Anything which can trap you. May refer to both physical and conceptual things.
1 – I’m stuck in the potential well of apathy right now.
2 – Sorry, the seminar later is a potential well. There’s no way I can get out of it.

Anything which is very old.
– I wouldn’t read that paper. It’s so old it’s actually redshifted.

n Sigma
(See Standard Deviation)
Anything which deviates significantly from normal (replace n with any integer). Used to describe something which is exceptional — with the number saying exactly how exceptional!
– This pizza is amazing! Like, 5 sigma!

Some Discrepancy
When things aren’t quite right.
– There’s some discrepancy between my memory of last night and how much money I have left in my wallet.

Standard deviation
Use when describing how close something is to being ideal.
– The pizza’s going to be a while longer, it’s still a couple of standard deviations away from being cooked.
– Come on, just a couple more minutes. I’m within one standard deviation of being ready to go out!

Compare your own timescale with another one to emphasise how quick or slow something is!
(See also Epoch).
– Sorry for the delay. Don’t worry. It’ll get done on a timescale short compared with the Hubble time.
– Look I know you think it’s really quick, but compared with the Planck time, this might as well be taking forever.

Vanishingly small
(See Negligible).

for Very small values of
Use when there isn’t enough of something.
(see also for Certain values of).
– There may be enough coffee left for three cups, but only for very small values of three.

Within an order of magnitude
Use as “close enough”.
– What? I was on time… To within an order of magnitude.

Within error bars
Similar to Within an order of magnitude, but not as close.
– I look just like Johnny Depp, within error bars.

Zero order approximation
Used to assume vaguely similar things to be the same. Useful for ignoring details (see Ideal Case) or if you just don’t care.
– “Hey, I asked for a pint of Guinness not a glass of wine.” “To a zero order approximation, they’re the same thing.”
Alternatively, a guess when you actually have no idea. An educated guess in an ideal case.
– When is everyone going to turn up? Well, to a zero order approximation… 8 o’clock?

(Huge thanks, by the way, to everyone who’s left comments and suggestions – and apologies that they got lost during the transfer to my new site here. You’re all brilliant!)

Actually, your friends will probably just think you’re incredibly geeky and give you funny looks, but with the kind of people I like to hang around with, that’s pretty much the same thing.

Also, PHD Comics is, as always frighteningly accurate…

Talk Like a Physicist Day originates here, and it seems many of the things in this phrasebook are also there – so chances are good they’re the original source for several of the things you’ll see here. Either that or it’s because physicists genuinely do speak like this…

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