1. ## Pound by pound

Could you please tell me What is the meaning of "pound by pound " in the following sentence:

＂It is estimated that pound by pound there are more bacteria on the Earth than all other life forms combined. ＂

Many thanks for your kind help.

2. ## Re: Pound by pound

(not a teacher)I've always heard the expression 'pound for pound' in sentences like this.It's an expression used in combat sports when comparing fighters of different weight classes. I think the author is trying to apply a similar concept here. Though they are small, bacteria far outnumber larger species.PS I'm sorry about the spacing. I don't think this site's word processor jives with my iPhone.

3. ## Re: Pound by pound

I agree, it's a confused phrase. He seems to be saying that they weigh more than all other life forms combined, in which case he should say that they do so "by weight" or "by the pound."

By saying "pound by pound" he is seeming to say that when you factor in their relative small size, there are more of them.

4. ## Re: Pound by pound

Originally Posted by SoothingDave
I agree, it's a confused phrase. He seems to be saying that they weigh more than all other life forms combined, in which case he should say that they do so "by weight" or "by the pound."
He should say that they do so "by (bio)mass", not weight. "Weight" is what most people say when they mean "mass". "Weight" is the force due to gravity and "mass" refers to the amount of matter.

5. ## Re: Pound by pound

In common use, such a fine distinction is not made. We're going to assume that you aren't weighing one on earth and the other on the moon.

6. ## Re: Pound by pound

Originally Posted by SoothingDave
In common use, such a fine distinction is not made. We're going to assume that you aren't weighing one on earth and the other on the moon.
OK, but if we're talking science here, then we should use the proper terms. Matter is simply not expressed in newton. This may sound pedantic, but I always like to use the proper terms, especially in scientific contexts (even though most people certainly do not always do this).

7. ## Re: Pound by pound

Originally Posted by Chicken Sandwich
OK, but if we're talking science here, then we should use the proper terms.
Fair enough, if we are talking science. Most of us in everyday life do not understand the difference between 'mass' and 'weight' and, once we have left school and science lessons don't know a newton from an apple.

I am not being flippant here. If we are writing in a science context, then the difference between 'mass' and 'weight' or 'newton' and 'kilogram' is vitally important. But, in this language forum, I think that we should acknowledge that most native speakers have no idea about such fine points.

ps (probably irrelevant ): As a sailor, I cringe when I hear people saying, "We were cruising at eight knots an hour". Even as a non-scientist, I blush if someone says, "This happened light years ago". However, and reluctantly, I have to accept that this is the way many people speak. It is not 'correct', but I venture to suggest that, in normal conversation, it is acceptable.

8. ## Re: Pound by pound

The learner of the English language should also recognize that in English customary units, a pound (force, lbf) is a pound (mass, lbm) in a way that a newton is not a kilogram. 10 lbm=10 lbf.

On Earth, with standard gravity.

9. ## Re: Pound by pound

Originally Posted by SoothingDave
The learner of the English language should also recognize that in English customary units, a pound (force, lbf) is a pound (mass, lbm) in a way that a newton is not a kilogram. 10 lbm=10 lbf.
I don't want to make a big deal out of it, but I'm confused by this statement. 10 lbm cannot equal 10 lbf because you have to multiply lbm by 32.174 049 ft/s2 to convert to lbf. See the following formula:

Moreover, two objects can have the same mass, but very different weights because mass is independent of acceleration but weight isn't.

Still, I don't see at all how 10 lbm can equal 10 lbf. Is this some kind of convention of physics that I'm not aware of? Please enlighten me if you feel like doing so .

Edit. I have found a link here that shows that you're right. I must admit that it's a strange convention and it makes little sense to me. And as you said, it's not done with kg/newton.

10. ## Re: Pound by pound

It's a matter of conventions. In the systems I work with a pound is a pound. See the Wikipedia article (which it seems you already have):

Pound (force) - Wikipedia, the free encyclopedia

In the gravitational systems, the weight of the mass unit (pound-mass) on Earth's surface is approximately equal to the force unit (pound-force). This is convenient because one pound mass exerts one pound force due to gravity. Note, however, unlike the other systems the force unit is not equal to the mass unit multiplied by the acceleration unit[8]—the use of Newton's Second Law, F = m·a, requires another factor, gc, usually taken to be 32.174049 lbm·ft/lbf·s2 = 32.174049 lbm/slug.

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