# Is there an example of an infinite signal? [closed]

In the real world, Is there an example of an infinite signal?

• You mean a signal that extends from $-\infty$ to $\infty$ in time? Hmmm, think about it for a moment. – Matt L. Dec 11 '18 at 17:03
• Imagine you could show a signal has existed from $t=-\infty$ (or from $t=0$ if you prefer)... How could you prove it will exist until $t=\infty$? – MBaz Dec 11 '18 at 17:11
• @MattL. No, a signal that extends from 0 to $\infty$ . but, I don't no. :( – niloofar jamshidi Dec 11 '18 at 17:14
• We can arbitrarily invent signals. For example, $s(t)=\sin(t)$ is infinitely long. Is that a real-world signal? I don't know – but if we say "the signal is the electric field strength of a plane electromagnetic wavefront over time, shot from earth into the vastness of space", that's a pretty real signal, and it's pretty infinite... – Marcus Müller Dec 11 '18 at 17:25
• @MBaz In physics, the energy is always existed. is not possible boute the signal ? – niloofar jamshidi Dec 11 '18 at 17:25