science-physics: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/science-physics - from package: science-physics

You may install the required package with command apt-get install {package}

Error in other languages:
science-physics: bevel nie gevind nie
science-physics: comandă negăsită
science-physics: comando não encontrado
science-physics: commande introuvable
science-physics: command not found
science-physics: käsku ei ole
science-physics: không tìm thấy lệnh
science-physics: komanda nerasta
science-physics: Kommando nicht gefunden.
science-physics: kommandot finns inte
science-physics: komut yok
science-physics: nie znaleziono polecenia
science-physics: níor aimsíodh an t-ordú
science-physics: no se encontró la orden
science-physics: no s'ha trobat l'ordre
science-physics: opdracht niet gevonden
science-physics: parancs nem található
science-physics: perintah tidak ditemukan
science-physics: príkaz nenájdený
science-physics: příkaz nenalezen
science-physics: команда не найдена
science-physics: командата не е открита
science-physics: 命令找不到
science-physics: コマンドが見つかりません